FIG. 1 of the accompanying drawings is a diagrammatic view in longitudinal cross-section of a straw for the preservation of a predetermined dose of liquid-based substance, in particular pure or diluted animal semen.
The straw 10 shown in FIG. 1 comprises a tube 11 and a stopper 12.
The tube 11 is conventionally made from extruded plastic material, with an inside diameter for example of 1.6 or 2.5 mm and a length of the order of 133 mm.
The stopper 12 is usually of the three-part type originally described in French patent 995 878, corresponding to British patent 669 265, i.e. formed by two plugs 13 and 14 made from a fibrous substance enclosing a powder 15 which, on contact with a liquid, is capable of transforming into an impermeable paste or gel adhering to the wall of the tube so that the stopper is liquid-tight.
In the initial state, shown in FIG. 1, the stopper 12 is arranged close to the end 16 of the tube 11 and it is provided that in the filled state, the dose of liquid substance which must be preserved in the straw 10 is placed between the stopper 12 and the end 17 of the tube 11 that is the furthest from the stopper 12.
In order to fill the straw 10, the end 16 is placed in communication with a vacuum source while the end 17 is placed in communication with a vessel containing the substance to be introduced into the straw.
The air initially contained between the stopper 12 and the end 17 is sucked through the stopper while the substance moves forward in the tube until it encounters the stopper 12, by the end 18 thereof that is turned towards the end 17 of the tube 11, that is to say the end of the stopper 12 that can be seen on the right in FIG. 1.
If necessary, the straw is welded close to one or both of its two ends 16 or 17 and is placed in cold storage.
In order to empty the straw 10, if necessary after cutting the welded end portions and thawing, there is inserted into the tube 11 a rod which comes to bear on the end 19 of the stopper 12 (which end is situated on the opposite side to the end 18). Using this rod, the stopper 12 is made to slide in the manner of a piston towards the end 17 or the end which corresponds after cutting the welded portion, which causes the expulsion of the dose of substance which had been introduced into the straw.
When the straw such as 10 is used for the artificial insemination of livestock, in particular bovine, ovine or caprine livestock, or rabbits, a reusable insemination syringe and a single-use sanitary sheath are used.
The insemination syringe comprises a rigid tubular body, for receiving the straw filled with semen, and comprises the rod for driving the stopper, slidingly mounted in the rigid tubular body.
Prior to insertion of the straw into the rigid tubular body, the rod is taken out or withdrawn as far as possible from the body at the proximal end, that is to say at the end which is manipulated by the inseminator during the operation, then the straw is inserted into the rigid tubular body at its distal end (the far end from the proximal end), the straw 10 being inserted with the end 16 of the tube 11 (the end closest to the stopper 12), first. The straw 10 is pushed into the rigid tubular body of the syringe until the end 16 of the tube 11 encounters a shoulder forming a pushing-in stop.
The straw 10 is then in place in the rigid tubular body of the syringe. The end 17 of the tube 11 as well as a certain length of the tube 11 starting from that end remain outside the rigid tubular body, that is to say that a certain part of the straw 10 projects beyond the distal end of the rigid tubular body of the syringe.
The sanitary sheath comprises a tube of which the inside diameter is such that the rigid tubular body of the syringe may be inserted therein. At one end (the proximal end) the tube of the sanitary sheath is open and at the other end (distal end) the sanitary sheath conventionally comprises a turned back edge forming a hem on the inside. Inside the sheath 3 a sliding sleeve member is disposed.
The rigid tubular body of the syringe, in which the straw was placed in advance, is inserted into the sheath by its open end with the straw first, the straw inserts into the sliding sleeve member and drives it. The insertion into the sheath ends when the sliding sleeve member and the straw come to bear against the hem-forming turned back edge situated at the distal end of the sheath (which is the far end to the open end of the sheath tube).
The sheath is then fastened to the rigid tubular body of the syringe, in general in the neighborhood of the proximal end of the sheath (open end of the tube) for example with a suitable ring.
The tube 11 of the straw 10 is thus immobilized relative to the assembly formed by the tubular body of the syringe and by the sanitary sheath fastened to that body, since the end 16 of the tube 11 bears against the shoulder of the tubular body of the syringe and the end 17 bears against the hem-forming edge of the sanitary sheath.
The assembly formed by the sanitary sheath and the syringe is then inserted into the animal and when that assembly is in place, the rod is used to make the stopper 12 of the straw 10 slide in order to eject the semen out from the tube 11 and out from the sheath tube by the aperture surrounded by the hem-forming edge.
The role of the sliding sleeve member is to provide liquid-tightness for the liquids between the straw tube and the sheath tube in order for the semen to be properly ejected out from the sheath (and not lost between the straw tube and the sheath tube).
French patent application 2 832 919, to which corresponds the United States patent US 2005/0107659 describes such a syringe and such a straw.
Sanitary sheaths are also known in which the sliding sleeve member and the hem-forming turned back edge are replaced by a tip attached to the tube by an insertion fit or by bonding
This tip comprises a tail inserted into an end portion of the tube and a head disposed in line with the tube.
For the insertion fit between the tail and the end portion of the tube, the tail comprises annular ribs on its outside surface, facing the inside surface of the tube; the head comprising a shoulder facing the rim of the tube and jutting relative to the base of the tail.
The tip comprises a duct opening into the tube at the proximal end of the tail (the far end of the tail from the head) and out of the sheath at the outside surface of the head.
This internal duct of the tip comprises a portion oriented in the axial direction, narrowing from the proximal end of the tail, configured in order for the portion of the tube 11 of the straw 10 situated in the neighborhood of the end 17 (furthest end from the stopper 12) can enter the narrowing portion of the duct and advance to a stop position in which the portion of the tube 11 situated in the neighborhood of the end 17 is clamped around by the wall of that portion of the duct.
This clamping round provides at the same time the stop for the pushing-in of the straw into the sheath and the liquid-tightness between the straw and the sheath.